W.E. Smith

The reactions of gold(0) with amino acids and the significance of these reactions in the biochemistry of gold

Abstract Gold(0) dissolves in a wide range of aqueous amino acid solutions exposed to dioxygen. In particular, the thiol-containing molecules cysteine, penicillamine and glutathione give solutions of gold complexes which can be identified by circular dichroism. Animal experiments suggest that gold complexes can be absorbed readily through skin. Gold concentration in human skin which had been in prolonged contact with gold and concentrations from the skin of patients treated with Myocrisin, a gold(I) compound, are reported. The possible significance of these results in terms of erosion of jewelry and skin-irritant reactions is discussed.

Copper schiff base complexes with polyfunctional amino acids

Abstract Amino acid Schiff base copper complexes of either salicylaldehyde or 2-hydroxy-1-naphthaldehyde with 1 -serine, 1 -histidine, histamine and 1 -tryptophan have been prepared by constituent combination. The amino acid part of the ligands coordinates to the copper through the carboxylate group and the other available functional group of the amino acids plays a more minor role as a blocking group or in intramolecular bonding. Schiff bases of salicylaldehyde or 2-hydroxy-1-naphthaldehyde with cysteine or penicillamine were prepared. In solution, NMR and IR evidence suggested thiazolidine ring formation in these bases and the presence of two conformers in the salicylidinecysteine base. Bases containing penicillamine produced a stoichiometric Schiffs base copper complex. Cysteine-containing ligands produced a stoichiometric compound with zinc but not with copper. However, with copper and not with zinc, constituent combination produced compounds of general formula, aldehyde (amino acid) 2 (copper) 2 xH 2 O. These latter compounds are believed to contain either cystine or dipenicillamine.

THE ELECTRONIC SPECTRA OF SOME GOLD(III) COMPLEXES

Abstract The electronic spectra of a number of gold(III) complexes with amine, phosphine and halide ligands have been measured. The positions and intensities of the lowest energy bands appear to depend on the nature of the complexing species and in particular a wide variation in intensity which was related to the nature of the complexing ligands was observed.

Exchange reactions between disulphides and myocrisin: An in vitro model for a mechanism in chrysotherapy

Abstract Disodium aurothiomalate or Myocrisin has been found to react with the disulphides, 5,5′-dithio-bis-(2-nitrobenzoic acid) - commonly known as Ellmans reagent - and lipoic acid. A new polymeric species (ESAu) x is identified in solution. Two specific reactions are discussed which result in the formation of mixed disulphide with Ellmans reagent and the formation of dithiomalate with lipoic acid. The gold nuclei are transferred to the incoming moiety with the result that the disulphide linkage is opened. The importance of this reaction for cellular function is discussed.

The electron spin resonance of copper(II) schiff base complexes containing amino acids as part of the ligand

Abstract The electron spin resonance of frozen solutions of a range of copper complexes of Schiff bases with amino acids as a component of the base have been measured at 110 K. The complexes appear to be of distorted planar structure with two nitrogen and two oxygen coordinating groups. They are sufficiently flexible for the degree of planarity to be affected by the coordinated solvent. Sharp fine structure on one compound was analysed in terms of a hyperfine interaction from copper, the azomethine nitrogen and its associated proton.

Some complexes of 2.3-Dimercaptopropanol (BAL) with gold(I) and gold(III)

Abstract 2, 3-Dimercaptopropanol (BAL) reacted with the tetrachloroaurate ion in solution to form a series of insoluble polymers of definite stoichiometry. Both gold(I) and gold(III) have been identified in these compounds. Reaction of BAL with the tetrabromoaurate ion and with thiomalic acid and D-penicillamine complexes of gold also produced insoluble precipitates. However, with an L-cysteine complex of gold no precipitate was isolated, although there was evidence of replacement of cysteine with BAL. The implications of these results for the use of BAL in cases of gold toxicity are discussed

The electronic spectrum of chromium(II) in a diamagnetic and a paramagnetic layer lattice host

Cr2+ ions can be doped into an MgCl2 layer lattice up to about an 18% replacement of Mg2+ with Cr2+. Electronic spectra show no evidence of Jahn-Teller distortion and indicate that the chromium site is centrosymmetric. Thus, the Cr2+ geometry is defined by the lattice. Both Mn2+ and Cr2+ nearest neighbours enhance the intensity of spin forbidden bands and Cr2+ in a paramagnetic MnCl2 host lattice shows a similar effect. Comparison with other systems suggests that the mechanism of exchange is dependent on the electronic structure of the neighbouring ions.